That depends of course how the transient/surge has been coupled into the mains. If that is due to a ligtning event at a short range, the impedance may be much less. Your analysis is right when the even has been generated far away.
Regards, Ing. Gert Gremmen, BSc . -----Oorspronkelijk bericht----- Van: John Woodgate [mailto:j...@jmwa.demon.co.uk] Verzonden: Saturday, September 07, 2013 11:35 AM Aan: EMC-PSTC@LISTSERV.IEEE.ORG Onderwerp: Re: [PSES] Spark Gap PCB Layout on AC Mains In message <FCA549BE3ECF9D4CB8CB8576837EA48920A1A4@ZEUS.cetest.local>, dated Sat, 7 Sep 2013, "ce-test, qualified testing bv - Gert Gremmen" <g.grem...@cetest.nl> writes: >Anyway, the primary circuit always need to be build for high surge >currents, > >and one should always insert induction to limit surge currents. > >As the impedance of the spark gap is low, only a small amount of >induction > >will reduce the surge current substantially Quite true, but the mains supply itself (unless it's from a very nearby private MV/LV transformer, has inductance of the order of a millihenry (0.3 ohms at 50 Hz), so there is not much point in adding only a few microhenrys. IEC TR60725 gives 'reference impedances' for various types of mains supply. While these tend to be higher than the actual impedance at the 'point of common coupling', they are a guide to the impedance at a typical wall-socket. This impedance limits the prospective short-circuit current. -- OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk If dictionaries were correct, we would only need one, because they would all give the same information. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <emcp...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <emcp...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
